Pipe Threaded Connection Solid Lubricant Coating Galling Resistance
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Solution Overview
Problem
Existing threaded connections for pipes or tubes in oil country tubular goods face challenges with low over-torque performance and galling resistance, particularly due to insufficient torque on shoulder resistance, which affects the repeated fastening and loosening processes without causing plastic deformation or galling.
Innovation Solution
A threaded connection with a solid lubricant coating layer containing a resin, a solid lubricant powder, and Cr2O3, applied to at least one contact surface of the pin and box, enhancing over-torque performance and galling resistance by adjusting the Cr2O3 content between 1.0 to 20.0 mass%, thereby increasing the torque on shoulder resistance and preventing galling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heavy metal-containing compound greases are used to improve galling resistance, then galling resistance is improved, but environmental harm increases due to heavy metal contamination
Solution Approach 1:
The invention extracts and removes the harmful heavy metal components (Pb, Zn, Cu) from the compound grease formulation while retaining the essential lubricating function through alternative solid lubricant materials, thereby eliminating environmental harm while maintaining galling resistance
Solution Approach 2:
The invention changes the chemical composition parameters of the lubricant by substituting heavy metal compounds with solid lubricant particles (graphite, MoS2, WS2, h-BN) having specific physical and chemical properties, achieving the same protective function without toxic substances
2Reliability
If the torque on shoulder resistance is increased to prevent plastic deformation during fastening, then over-torque performance is improved, but the fastening torque adjustment becomes more difficult
Solution Approach 1:
The invention changes the friction characteristics at the shoulder interface by applying solid lubricant coating, which modifies the torque distribution during fastening and creates a more favorable difference between shouldering torque and yield torque, thereby improving over-torque performance while maintaining adjustability
3Reliability
If solid lubricant coating layer is applied to improve galling resistance and over-torque performance, then both galling resistance and over-torque performance are improved, but the manufacturing complexity increases
Solution Approach 1:
The solid lubricant coating is applied in advance to the contact surfaces before the threaded connection is assembled and used, preparing the surfaces with protective properties beforehand to prevent galling and control torque characteristics during subsequent fastening and loosening operations
Solution Approach 2:
The invention uses composite material structures by combining solid lubricant particles (graphite, MoS2, WS2, h-BN) with a binder resin to form a coating layer that integrates multiple functional properties (lubrication, adhesion, wear resistance) into a single applied layer, simplifying the overall system while achieving multiple performance goals
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution significantly improves over-torque performance and galling resistance, allowing for multiple cycles of fastening and loosening without galling, with the Cr2O3 content in the solid lubricant coating layer providing a high torque on shoulder resistance and maintaining the environmental sustainability by avoiding heavy metal-based greases.
Implementation Method 1
The threaded connection for pipes or tubes includes a solid lubricant coating layer on at least one of the contact surfaces of the pin and the box. The solid lubricant coating layer contains a resin, a solid lubricant powder and Cr2O3 in a range of 1.0 to 20.0 mass %.
Data Source
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AI summary
This invention provides a threaded connection for pipes or tubes having high over-torque performance, and a method for producing the threaded connection for pipes or tubes. A threaded connection (1) for pipes or tubes according to the present embodiment includes a pin (5) and a box (8). The pin (5) and the box (8) include a contact surface (6), (9) including a threaded portion (4), (7) and a metal contact portion. The threaded connection (1) for pipes or tubes includes a solid lubricant coating layer (21) on at least one of the contact surfaces (6), (9) of the pin (5) and the box (8), the solid lubricant coating layer (21) including a resin, a solid lubricant powder, and Cr2O3.